The present invention relates to a logic controlled method of tuning signals and/or deviations in a radio telephone having a logic section controlling its operation, and the use of this method in series production and maintenance. The invention also relates to a radio telephone, tuned with a method according to the invention.
In a radio telephone some signal levels and deviations must be kept within the adjusted value under all conditions, independent of temperature. Some of these signals include for example the low frequency level of the receiver, the deviation of the transmitter or of the control signal, etc. The signals pass through e.g., amplifiers, filters, detector circuits, mixers and modulators. Temperature causes amplification changes or deviations in all of these stages. The most common approach in the prior art is to accept these changes, and to compensate them by temperature dependent resistances such as NTC and PTC resistors.
However, this approach has proved to be a poor solution because some circuits, such as filters and detector circuits, behave differently in different temperatures, and it is not possible to fully predict the changes. The variations of the compensating component tolerances also affect on the changes.
The prior art solution was to accept a poorer yield in production, or to use better quality components. Both alternatives lead to increased production costs and moreover, the better quality components may increase the size and power consumption of the radio telephone, and thus impossible to use in small sized handsets.